The present invention relates generally to the field of mixing water and emulsion polymers and more particularly to mixing water and water-soluble emulsion polymers having water-polymer gel particles suspended in oil with the aid of surface active dispersants to produce a homogeneous mixture.
Water-soluble polymers may be anionic, cationic or non-ionic. These polymers are used either alone or in combination with other aids in the coagulation and flocculation of water-insoluble particles suspended in an aqueous medium. More specifically, these polymers are used as flocculants or coagulation aids in the clarification of water, dewatering of sludges and in certain process applications. When dissolved in water, these polymers uncoil into very long extended molecules which function to bridge the suspended particles together to improve liquid-solids separation in the water.
The water-soluble polymers may be produced in a dry powder form and then mixed with water when the polymers are needed for use. As an alternative to producing the dry powder form, some of these polymers are supplied in an emulsion form. In the emulsion form, water-polymer gel particles or dry polymer particles are suspended in oil with the aid of surface active dispersants or surfactants. The surface active dispersants or surfactants are used to create and maintain a stable emulsion. Other dispersants or surfactants are added to the emulsion to disperse the oil phase in the water phase when the emulsion polymer is diluted with water.
In order to effectively utilize the water-soluble emulsion polymers, these polymers are diluted with water to produce a solution having maximum viscosity for any given concentration. Generally, a solution having a concentration of the emulsion polymer greater than about 1% will resemble a gel and, as can be appreciated, will be made virtually unusable for the purpose. It is believed that during the procedure of diluting the emulsion polymers with water, sufficient mixing must occur or enough mixing energy must be supplied to displace the dispersants or surfactants from the surface of the water-polymer gel particles to allow the water to penetrate the gel/oil interface so that the polymer will contact and dissolve in the water phase. The other dispersants or surfactants present in the emulsion then disperse or emulsify the oil in the water phase. Thus, a viscous homogeneous mixture or solution is produced with activated polymer which is ready to use for the purpose. However, if too much mixing or agitation occurs during the dilution procedure, the dissolving polymer molecules will be sheared into smaller molecules, thereby resulting in a damaged polymer product which is ineffective to use. If too little mixing or agitation occurs during the initial dilution procedure, the dispersants or surfactants that are present to emulsify the oil carrier will disperse that oil even though the oil still contains some water-polymer gel particles. These particles are, in effect, encapsulated in the oil that is then dispersed in the water. The encapsulated gel particle cannot thereafter dissolve. If sufficient mixing is later performed to break the encapsulation, the polymer molecules that have already dissolved in the water will be sheared or broken. As a result, the final viscosity of the solution will never reach the maximum potential and performance of the polymer will correspondingly drop.
Various apparatus are commercially available for mixing water-soluble emulsion polymers and water together to produce a homogeneous mixture. Such apparatus make use of mixing chamber devices, pumping devices, or static mixing devices to mix the emulsion polymers and water. However, the present inventors have found that different emulsion polymers require different amounts of effective mixing energy. While the prior art apparatus may be suitable for mixing certain emulsion polymers, such apparatus are generally unsuitable for effectively mixing other emulsion polymers since such apparatus may provide either too much mixing energy or too little mixing energy for these other polymers. The amount of water and the amount of emulsion polymer that goes through such devices may be varied, but such apparatus suffer from the disadvantage that such devices provide a fixed amount of mixing or mixing energy. The amount of mixing energy supplied by such apparatus upon initial dilution of the polymer with water generally cannot be adjusted to obtain the optimum mixing energy for different polymers so that maximum activation of the mixture is achieved for each polymer. That is, such apparatus cannot be adjusted to supply optimum mixing for various emulsion polymers to sufficiently mix each polymer and water to displace the surface active dispersants from the water-polymer gel surface to allow the water to contact the polymer and to dissolve the polymer in the water, upon initial dilution of the polymer with water, without causing the polymer molecules to shear into smaller polymer molecules.